In recent years, information terminal equipment including personal computers and servers, and communication equipment, such as Internet routers and optical communication, have been required to process massive information at high speed, and the speed and frequency of electrical signals have become higher. With this, in addition to conventionally required properties such as flame retardancy, heat resistance, and peel strength with copper foil and the like, lower dielectric constant and lower dielectric loss tangent have been required of printed wiring board materials used in the equipment. In order to meet the requirement of these properties, various attempts have been made in the formulation of resin compositions.
In order to provide electrical properties to such materials, a method of incorporating, in a resin composition, a resin having a low dielectric constant and a low dielectric loss tangent, such as a fluororesin, a cyanate ester resin, a polyphenylene ether resin, or a vinyl compound mainly comprising styrene, is known (for example, see Patent Literature 1). However, generally, a laminate using such a resin or compound has poor flame retardancy, and therefore, in order to provide high flame retardancy, it is necessary to contain a halogen-based compound in the resin composition (for example, see Patent Literatures 2 and 3). But, when a halogen-based compound is used, environmental problems arise, for example, harmful substances, such as dioxin, may be generated during burning.
Therefore, as other methods for increasing flame retardancy, for example, studies of adding a compound containing phosphorus or nitrogen to a resin composition are made (for example, see Patent Literatures 4 and 5). However, in the case of a nitrogen-containing compound, harmful nitrogen oxide may be produced, and in the case of a conventionally used phosphorus-containing compound, a problem is that as the amount of the phosphorus-containing compound added is increased in order to provide high flame retardancy, the heat resistance deteriorates, that is, the glass transition temperature (Tg) of the resin composition decreases (for example, see Patent Literatures 6 and 7).